It has long been known that fuel is used more efficiently by an internal combustion engine if mixed with very humid air. There was a period in the early history of motor car development when attempts were made to design "water injection" into fuel supply systems. While the use of water injection never enjoyed commercial acceptance, it was often used to enhance the performance of racing cars. The practice was to atomize water and to inject it into the air-fuel mixture. The "water-in-the-fuel" concept was not very salable. As fuel became more readily available, motor car makers directed their efforts elsewhere. Engine and fuel development advanced, but water injection did not.
Recently, interest in the practice was revivied by the development of a system which utilized a vacuum operated supplemental air supply device to mix air with small quantities of water to be drawn into the carburated fuel flow of gasoline engines. The supplemental air device was taken from the supplemental air inlet art. One example is shown in U.S. Albano-Harren Pat. No. 3,946,710. Such devices, and this example, comprises a normally spring opened valve for connection in a flowpath which extends from open air to the inlet manifold at a point just downstream from the carburetor. The manner of their operation is shown in a graph in the patent.
The combination of the air inlet device in parallel with a water source has been very successful for certain types of vehicle use in Europe and in Africa, particularly in more arid regions. The advantage offered is provided only under limited speed and load conditions. In practice, the system has not been as important in improving passenger car performance as it has been for vehicles which are operated at lower speed with periods of idling, as occurs in delivery services and some kinds of governmental service operations.